Thanksgiving is an annual holiday which is celebrated on Vinland and the Isle of Berk. In Vinland, the holiday is very similar to modern day Thanksgiving, but Berkians are forced to celebrate the holiday with little understanding of its traditions.
Upon returning from his expedition to Vinland, Leif Erikson brought back stories of the Thanksgiving traditions of the people to the Barbaric Archipelago. However, lacking many essentials of the Thanksgiving holiday in Vinland, including pumpkins or turkeys, the Vikings of Berk were forced to celebrate the holiday with only the most basic understanding of the Vinland traditions.
Fishlegs Ingerman later developed a particular love for the holiday and obsessively studied the people of Vinland in order to celebrate Thanksgiving in the most accurate manner possible. However, as very little was known to the Vikings about the people of Vinland, even his research contained several holes.
Fishlegs understands the Thanksgiving holiday as being a celebration of feasting for the sake of feasting. Months in advance of the holiday, he trains himself in overeating endurance trials until nauseous, hoping to expand the capacity of his stomach so as to handle as much food as possible during the holiday
During the Thanksgiving holiday, Fishlegs dresses up Meatlug as a turkey, mistakenly believing that the turkey is a bird of prey and thus believing that Meatlug will become more terrible and imposing in battle if she is dressed as one.